Thank you for your advice.  I will try this and see what happens!

thanks again,
thomas


>From: Michael Rigby-Jones <mrjones@NORTELNETWORKS.COM>
>Reply-To: pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
>To: PICLIST@MITVMA.MIT.EDU
>Subject: Re: [PIC]: SPI routine for 16F84 slave mode
>Date: Mon, 23 Apr 2001 08:11:46 +0100
>
>3 wire slaves (such as SPI) detect the state of the data line on either the
>falling or rising edge, so you shouldn't need a delay in your interrupt
>handler.  The state of the data should be stable when the clock edge is
>detected.
>
>You don't need to have a timeout, a 3 wire bus uses a Chip Select (CS)
>line.
>In your interrupt service routine you can read the state of the CS line,
>and
>if it is active (usualy active low) then shift in your data.  If it is not
>then reset you shift register routine.  This way, if a transmission is
>aborted part way through, you won't be left with half of the data in your
>shift register.
>
>If you decide to use polling instead of interrupts, this will either
>severely limit your maximum bus speed or what else you can do at the same
>time.
>
>Regards
>
>Mike
>
> > -----Original Message-----
> > From: Thomas N [SMTP:thomasn101@HOTMAIL.COM]
> > Sent: Monday, April 23, 2001 7:27 AM
> > To:   PICLIST@MITVMA.MIT.EDU
> > Subject:      [PIC]: SPI routine for 16F84 slave mode
> >
> > Hi everyone,
> >
> > I wrote a SPI routine for the 16F84 master mode only before and it works
> > great.  I am stuck at writing the SPI routine for the 16F84 slave mode.
> >
> > I don't want to write the code with clock frequency-dependant (I mean I
> > don't want fixed input clock frequency).
> >
> > I was thinking of detecting the level change (use interrupt?), delay a
> > little bit, and take the sample.  But "delay a little bit" limit the
>input
> > frequeny.  And what if the master stops in the middle of the
>transmition?
> > The way I wrote the code, it will stuck (keep waiting for the master to
> > send
> > enough clock cycle - it expects 8 bits before the subroutine exits)  I
>am
> > not sure how to write the timeout routine.
> >
> > Please help me or give me a link to the SPI routine (I searched at
> > piclist.com, but couldn't find anything useful).  It would be ideal if
> > there
> > is a code which can do both transmit and receive (master or slave mode)!
> >
> > Thank you in advance
> > Thomas
> >
> >
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